All GMAT Math Resources
Example Questions
Example Question #3171 : Gmat Quantitative Reasoning
Two dice are thrown and their sum is noted. One is fair and one is loaded but both have the usual numbers 1-6 on their faces. Which, if either, is greater - the probability of tossing a 3 or the probability of tossing an 11?
Statement 1: The probability of tossing a 2 on the loaded die is 0.2.
Statement 2: The probability of tossing a 5 on the loaded die is 0.3.
Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.
Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.
BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.
EITHER statement ALONE is sufficient to answer the question.
BOTH statements TOGETHER are insufficient to answer the question.
BOTH statements TOGETHER are insufficient to answer the question.
A 3 can be rolled only by tossing a 1-2, but the loaded die can be either the 1 or the 2; similarly, an 11 can be rolled only by tossing a 5-6, but the loaded die can be either the 5 or the 6. We know only the probability of the loaded die coming up 2 and that of it coming up 5; we do not have this information for 1 or 6. We explore two cases and compare the probabilities of rolling a 3 and rolling an 11.
Case 1: Suppose the loaded die will come up 1 with probability 0.1 and 6 with probability 0.3. The probabilities of rolling a 3 or a 11 are, respectively:
and
making 11 the more likely outcome.
Case 2: Suppose the loaded die will come up 1 with probability 0.3 and 6 with probability 0.1. The probabilities of rolling a 3 or a 11 are, respectively:
and
making 3 the more likely outcome.
Therefore, the two statements together provide insufficient information to answer the question.
Example Question #74 : Arithmetic
Some balls - some completely red, some completely yellow, the rest half red and half yellow - are placed in a large box, and a ball is drawn at random. Which probability is greater - the probability of drawing a ball that is at least partly red, or the probability of drawing a ball that is at least partly yellow?
Statement 1: The ratio of balls that are half red and half yellow to balls that are completely red is .
Statement 2: The ratio of completely yellow balls to completely red balls is
BOTH statements TOGETHER are insufficient to answer the question.
BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.
Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.
Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.
EITHER statement ALONE is sufficient to answer the question.
Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.
Let be the balls that are completely red, completely yellow, and bicolored, respectively; let be the total number of balls. Then the probabilities of drawing a ball with some red and drawing a ball with some yellow are, respectively,
and
For the former probability to be greater than the latter, we can use some algebra to reveal:
That is, the former probability is greater than the latter if and only if there are more completely red balls than yellow balls. Similarly, the former probability is less than the latter if and only if there are fewer completely red balls than yellow balls.
Therefore, Statement 1 is irrelevant; Statement 2, which compares the number of completely red balls and completely yellow balls, gives us our necessary and sufficient information.
Example Question #3172 : Gmat Quantitative Reasoning
Two fair dice are tossed. What is the probability that the difference of the two numbers will be 1?
The difference of the two dice will be 1 in case any of the following outcomes occur:
This is ten outcomes out of a possible 36, so this yields a probability of
.
Example Question #25 : Discrete Probability
For Data Sufficiency questions, select either A, B, C, D, E based on the following rubric:
- A) statement 1 alone is sufficient, but statement 2 alone is not sufficient to answer the question
- (B) statement 2 alone is sufficient, but statement 1 alone is not sufficient to answer the question
- (C) both statements taken together are sufficient to answer the question, but neither statement alone is sufficient
- (D) each statement alone is sufficient
- (E) statements 1 and 2 together are not sufficient, and additional data is needed to answer the question
When a delectable baked treat is selected at random from the baker's case, what is the probability that it will be kirsch flavored?
1. One half of the treats are peanut-butter flavored.
2. There are one third as many kirsch treats as peanut-butter treats.
D
C
A
B
E
C
Remember, you do not have to SOLVE the data sufficiency problems. In other words, you do not have to calculate the exact probability of getting a kirsch-flavored (cherry liquor) treat. You just need to determine how many of the statements are NECESSARY to derive the answer.
The first statement by itself is not sufficient, because knowing that half of the treats are peanut butter flavored does not tell you the proportion that are kirsch flavored.
The second statement is not sufficient, because comparing the proportion of kirsch treats to peanut-butter treats won't help you find the probability of getting a kirsch treat unless you know the ratio of peanut-butter treats in the case.
But, if we put the two pieces of information together, we can solve the problem. Statement 1 tells us the proportion of peanut-butter treats, and statement 2 tells us how many kirsch treats there are compared to peanut-butter treats.
Therefore, the correct answer is C.
Example Question #1061 : Data Sufficiency Questions
Anna is about to pick a fruit for her snack from a basket of apples and oranges. What is the probability Anna picks an apple?
(1) The basket contains fruits.
(2) Half of the fruits in the basket are oranges.
C: BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient
B: Statement (2) ALONE is sufficient, but statement (1) ALONE is not sufficient
E: Statements (1) and (2) TOGETHER are not sufficient
A: Statement (1) ALONE is sufficient, but statement (2) ALONE is not sufficient
D: EACH statement ALONE is sufficient
B: Statement (2) ALONE is sufficient, but statement (1) ALONE is not sufficient
Let P(A) be the probability of Anna picking an apple and P(O) be the probability of Anna picking an orange. We need to evaluate each statement individually first:
(1) gives us the total number of fruits, but no indication as to the number of each fruit, so we cannot determine probabilities form (1) alone
(2) gives us the proportion of oranges. Let N be the total number of fruits, A the number of apples and O the number of oranges. We have:
We also know that .
We can rewrite this last equation as follow:
or
We know that P(A) = A / N and from statement (2) we get
which we can simplify to find P(A)
Therefore the right answer is B.
Example Question #1062 : Data Sufficiency Questions
What is the probability that a randomly selected person in a sample of 100 adults is left handed?
(1) The number of left handed adults in the sample represents one fourth of the number of right handed adults in the sample.
(2) All of the women in the sample are right-handed.
Statement (1) ALONE is sufficient, but Statement (2) ALONE is not sufficient
Statement (2) ALONE is sufficient, but Statement (1) ALONE is not sufficient
Both statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient
Each statement ALONE is sufficient.
Both statements TOGETHER are not sufficient.
Statement (1) ALONE is sufficient, but Statement (2) ALONE is not sufficient
Using Statement (1), we can write the following equation:
Let x be the number of left handed people in the sample. 100-x is then the number of right handed people in the sample.
Therefore, the probability that a randomly selected person in the sample is left handed is:
Therefore Statement (1) is sufficient to answer the question
Statement (2) indicates that all women in the sample are right handed. This statement is not useful as it does not give the total number of right handed people in the sample.
Therefore, Statement (2) is not sufficient by itself to answer the question.
Only Statement (1) ALONE is sufficient.
Example Question #1063 : Data Sufficiency Questions
One of the managers in a certain company is to be selected at random to represent the company at a national conference. What is the probability that a woman will be selected to represent the company?
(1) One third of the managers in the company are women.
(2) Half of the employees in the company are women.
Statement (1) ALONE is sufficient, but Statement (2) ALONE is not sufficient.
Statements (1) and (2) TOGETHER are not sufficient.
Each Statement ALONE is sufficient.
Both statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
Statement (2) ALONE is sufficient, but Statement (1) ALONE is not sufficient.
Statement (1) ALONE is sufficient, but Statement (2) ALONE is not sufficient.
(1) One third of the managers in the company are women.
Therefore the probability that the manager selected at random is a woman is .
Statement (1) alone is sufficient.
(2) Half of the employees in the company are women.
Even though half of the company's employees are women, this statement doesn't give the proportion of women who hold a manager job. Therefore, Statement (2) is not sufficient.
Example Question #32 : Discrete Probability
What is the probability that a randomly selected employee at a company have a MBA degree?
(1) Employees have a MBA degree.
(2) percent of employees do not have a MBA degree.
Statement (1) ALONE is sufficient, but Statement (2) ALONE is not sufficient.
Each Statement ALONE is sufficient.
Statements (1) and (2) TOGETHER are not sufficient.
Statement (2) ALONE is sufficient, but Statement (1) ALONE is not sufficient.
Both statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
Statement (2) ALONE is sufficient, but Statement (1) ALONE is not sufficient.
(1) 150 Employees have a MBA degree.
Since we do not know the number of employees at the company, we cannot determine the probability of employees who have an MBA degree. Statement (1) is not sufficient.
(2) 70 percent of employees do not have a MBA degree.
We can then determine the percentage of employees with an MBA degree as 30 percent. Therefore the probability of employees who have an MBA degree is 0.3.
Statement (2) ALONE is sufficient.
Example Question #33 : Discrete Probability
An insurer is trying to determine the probability of policyholders who had an accident this year.
(1) Of all policyholders, did not have an accident.
(2) Of the policyholders who had an accident, received a claim payment.
Both statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
Statement (1) ALONE is sufficient, but Statement (2) ALONE is not sufficient.
Statements (1) and (2) TOGETHER are not sufficient.
Each Statement ALONE is sufficient.
Statement (2) ALONE is sufficient, but Statement (1) ALONE is not sufficient.
Statement (1) ALONE is sufficient, but Statement (2) ALONE is not sufficient.
(1) Of all 1200 policyholders, 1050 did not have an accident.
From statement (1), we can determine that 150 policyholders had an accident. We can then calculate the probability as .
Statement (1) alone is sufficient.
(2) Of the policyholders who had an accident, 90% received a claim payment.
Statement (2) is irrelevant since we are not interested in the probability of policyholders who received a claim payment.
Statement (2) is not sufficient.
Example Question #34 : Discrete Probability
A store owner is trying to determine the probability of defective light bulbs he holds in his inventory.
(1) out of light bulbs are defective.
(2) After checking half of the inventory, the store owner finds defective light bulbs.
Statements (1) and (2) TOGETHER are not sufficient.
Statement (1) ALONE is sufficient, but Statement (2) ALONE is not sufficient.
Statement (2) ALONE is sufficient, but Statement (1) ALONE is not sufficient.
Both statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
Each Statement ALONE is sufficient.
Statement (1) ALONE is sufficient, but Statement (2) ALONE is not sufficient.
(1) 15 out of 150 light bulbs are defective.
Using statement (1), the probability of defective light bulbs is
Statement (1) is sufficient.
(2) After checking half of the inventory, the store owner finds 10 defective light bulbs
We do not know the number of defective light bulbs in all the inventory and we do not know the number of light bulbs in inventory.
Statement (2) is not sufficient.